Treatment of oils corrosive to copper



Patented Oct. 24, 1950 TREATMENT or one CORROSIVE T COPPER Charles A.Cohen, Roselle Park, NI J., assignor to Standard Oil Develo ration ofDelaware pment Company, a cor o- No Drawing. Application October 4,1946,Serial No. 701,087 7 This invention relates to the treatment ofpetroleum hydrocarbons particularly of the white oil type which, duringtheir preparation, have been 'acid treated to remove'undesirable'constit ue'ntssuch as olefins, aromatics and thelike, and,more particularly, to acid-treated oils which after neutralization andcontacting with or per colation through clay are found to be corrosiveto copper.

This invention describes a process for the treatment of mineral oil,petroleum products, and process lubricants'which are corrosive to thecopper strip as described in the Federal Standard Stock Catalog VV-L-79lC, Section IV, Part 5, Method 530.31.

Acid treatment of various petroleum hydrocarbons is a well establishedart and varies with the character of the particular hydrocarbon and itseventual use. For example, low boiling hydrocarbons from cracked stocksboiling in the gasoline range are treated with small percentages ofsulfuric acid varying in concentration from 95-98% for the purpose ofremoving and polymerizing the more reactive olefinic types of materialsand, after caustic washing, the material is generally rerun and cut tospecification boiling point. The purpose of this treatment is to removethe gum-forming constituents of the gasoline and improve the storagestability of the product. Desulfurization is generally accomplished atthe same time. Higher boiling hydrocarbons, such as kerosene, may belightly acid treated with weak concentrations of sulfuric acid on orderto improve burning quality and odor or may be highly acid treated withstrong acids, varying from 100% sulfuric acid to fuming sulfuric acidcontaining 20% by weight of sulfur trioxide. Kerosene treated withstrong acids are used'as deodorized bases for the preparation ofhousehold insecticides. Oils of the white oil type such as medicinaloils, cosmetic oils, transformer oils, refrigerator oils, hydraulicoils, and the like, usually require severe acid treatment and during theprocess of their refining are subjected to the action of concentratedsulfuric acid varying in strength from 98% to fuming sulfuric acid.Depending on the crude source. and the nature of the acid treatmentused, these oils.

when finished may at times be corrosive whentested with the copper striptest.

One of the objects of this invention is to render highly acid-treatedpetroleum hydrocarbons noncorrosive to copper.

Highly acid-treated oils or white oils are prepared by the drasticacid-treatment with sulfuric 2 acid. of a hydrocarbon cosity in therange of 30-1000 secondssaybolt at 7F. Prior'to treatment with fumingsulfuric acid; thefoil may be previously solvent extracted,

dfeasplialted, dewaxe'd, or" lightly acid treated to. remove" certainundesirable constituents. In

treating with the acid, it is usual to apply the acid in v a number of.dumps' during which mechanical or air agitation "is used. Between"successive' dumps'the mixture is allowed to settle and thesludge'drawn-oif anddiscarded. Dur' ing' the processof acid treatment, asubstantial quantity of oil-soluble sulfonic acids'known as mahoganyacids are formed and largely remain dissolved inthe oil. Prior to"finishing the oil, these mahogany acids must be removed either bywashing with water or immiscible solvent inthe acid state orthey may bepartially or Wholly neutralized with'a neutralizing agent such as'the;oxide, hydroxide'and carbonate of the alkali, and

alkaline'e'arth metals, and of ammonium, amines,

'etcl andf extracted withwa'ter or dilute alcohol in the former theirsalts'commonly known as" mahoganysoaps. The oila'fter removal of theacidic constituents and after "steaming to remove any volatile solvent,if present, but before contacting" with or percolation through clay,isknown asa"neutral oil. Depending onthe initial character of the oil,the'strength of the acid used,"the'temper'atureof the acid treatment,and

the. total quantit'y'of'acid supplied, the neutral: oil willvary incolor from about a 10 to a +27 saybolt color. The colored materialremaining in the oil may be hydrocarbon or resinous in nature or mayconsist of high molecular weightsulfonates which are diflicult'to removeby ordinaryextraction. It'is the purpose of contacting with orpercolation through clay to remove the last remaining c'olored'materialto yield a water; white oil having a Saybolt color of +30 and up. Alongwith color removal, the oil is improved in taste and odor and otherquality specifications such as susceptibility to oxidation'andresistance toformation of ran'cidity when exposed to ultra violet light.

' Very 'often'distillates and neutral oils'willhavel afgoodcopper testbut on processing the neutral" oil with clay a poo'rcopper testdevelops. 7 case of' the distillate, the presence of small amounts ofQrg'anic'acids such as naphthenic acid act as passivatin'g materials forthe surface of the copper and mask the true corrosive character of theoil. In the case of the neutral oils,

the presence of small amounts of sulfonic acids" or' mahogany soaps actin a similar manner on distillate having a visof often causing the oilto go 011 color and off taste in the medicinal grades.

The major object of this invention is to treat an acid-treated petroleumhydrocarbon either in its neutral state or finished state (that is,after treatment with clay) so as to improve the corrosion test whentested with copper.

I have now found that a satisfactory degree of improvement may beobtained by heating and mixing these neutral oils, which are corrosiveto the copper test, with solutions of alkali metal chlorites,particularly sodium chlorite. The alkali metal chlorite is used in anaqueous solution which may vary in strength between .02 and l .0 weightper cent, preferably 0.1 weight per cent; and is applied to the oil in avolume from 2% to preferably 10%. The choice of concentration is bestdetermined by the nature of the oil for example, its density, viscosityand tendency to form emulsions. For purposes of my invention, I havefound that sodium chlorite obtained commercially is suitable. Otheralkali metal chlorites and alkaline earth metal chlorites could be used,but on the basis of cost and availability, sodium chlorite is chieflyemployed.

' The time necessary to complete the reaction is considerably shortenedby the use of increased temperature. I have found that a temperature offrom about 40 C. to above about 100 C. is adequate, however, atemperature of 80 0. appears most practical. If, however, more rapidseparation is required, higher temperatures may be used. In certaininstances, it may be desirable to work at superatmospheric pressure, forexample, in treating the lower boiling acidtreated material, it may bedesirable to use superatmospheric pressures to keep the reactants in theliquid phase. Mechanical agitation, for example, by turbo-mixers, can beused or the oil may be treated in a tank in which a pump picks I upaqueous solution of the chlorite, passes it through a heat exchanger toincrease the temperature of the solution and brings it into a mixer toaccomplish intimate contact of the two phases.

' The length of contact between the oil and aqueous chlorite solutiondepends on the degree of corrosiveness present. For the usual amount ofcorrosion encountered, the time will vary from 20 minutes to 4 hoursdepending on the temperature used and the effectiveness of mixing andthe concentration of the chlorite. They are all variables bestdetermined by test.

I have found that any emulsions formed by this treatment break readilyon standing and the treated oil may be readily separated by knownmethods. After separation of the treated oil from the chlorite, the oilmay be finished where required by additional water washing and/orcontacting with or percolation through clay or, in the case of technicaloils where the degree of refinement required is not as severe asfor themedicinal grades of oil, may be brighte'ned by blotter pressing througha filter press. Ifeutral oils treated in this manner exhibit no assm 4corrosive action on copper, either in the neutral state or in thefinished state after percolation through clay.

While I have disclosed treatment with chlorite on the neutral oil, thesame treatment may be used on a finished oil where it is found thefinished oil is corrosive to copper. When used on a finished oil, theoil may be further finished after treatment with the chlorite by filterpressing or by repercolation through clay.

In those cases where the corrosion on copper is unusually severe, it hasbeen possible to dissolve the black coating obtained on the surface ofthe copper with acid and demonstrate that the black coating ispredominantly copper sulfide. Experimental evidence has shown that thepure organic sulfides such as the dialkyl sulfides, di-

aryl sulfide and alkyl aryl sulfides may be added to. a non-corrosiveoil in a small amount without corrosiveness being imparted to that oil.However, when elemental sulfur in concentrations as low as one part permillion is added to the oil or where a compound containing sulfur is alabile form such as a polysulfide linkage is added to the oil, corrosionwill be exhibited in the oil due to the tendency of the labile sulfur orelementalsulfur to react under the catalytic influence ofthe copper andform hydrogen sulfide and other corrosive sulfur compounds. I have nowfound that the use of alkali metal chlorites under the conditionsdisclosed above is particularly effective in decomposing and removingall types of sulfur when presentin either a free or labile form.

While no limitation is to be had to the theory of reaction, it isbelieved that the mechanism of treatment involves oxidation of sulfur,sulfide or polysulfide to sulfuric acid during the course of treatmentand subsequent fixation of the sulfuric acid by alkali or removal bywater washing.

The copper strip test mentioned above consists in polishing a strip ofthin copper sheet measuring /2 in. x 3 in. with a fine abrasive,immersing the copper strip in the oil to be tested and heating for 3hours in a steam bath at a. temperature of 212 F. The results are ratednumerically as follows: (1) shows no change in appearance of theoriginal copper strip; (2) shows a slight discernible yellow color butis still passable; (3) which does not pass (D. N. P.), shows apronounced bronze coloration; (4) shows a deep bronze to red color; (5)blue-black. In severely corrosive oils the copper may have a peacock huechanging to a brassy or silvery appearance. These silvery corrosive oilsare rated number 6 to 10.

My treatment produces improved quality tests. For example, taste andodor are improved, ability to resist deterioration by sunlight isimproved. susceptibility of the oil to oxidation is decreased, thephysical properties of the oil remain unchanged and, of course,corrosion to copper is substantially decreased. i

All types of oils may be treated by my method particularly parafiinicand naphthenic type oils.

In high viscosity oils which are acid-treated, there is encountered apolysulfide type of corrosive sulfur which usually exhibits an orange toreddish copper strip. In the lower viscosity oil range, that is, withkerosenes and gas oils, which are acid-treated, there is encountered afree sulfur type of corrosive sulfur which usually exhibits a copperstrip varying in hue from peacock hue to a black scaly deposit. Thelatter indicates a severe type of corrosion. Where indications are 76that the latter typeof corrosive sulfur is present,

I find'zthat the condition *issbbrrectd by'treatment of .the corrosiveoil with-sodium chlorite.

While -not bound by any mechanism whereby the corrosivesulfur isremoved, 'I may say that .a possible mechanism is the oxidation of thesulfur by sodium chlorite to sulfuric acid, and fixation of the sulfuricacid with alkali normally present in commercial sodium chlorite (sodiumchlorite commercially contains about .of sodium carbonate),or which :maybeextraneously added. The-oil-may be left in the acidstate and theacidity removed prior to finishing by water washing or other means.

It has long been known in the art to treat certain hydrocarbon oils withhypochlorite solutions. The development of the art of treating withhypochlorites is well summarized in Chemical Refining of Petroleum by V.A. Kalichevsky and B. A. Stagner, Second Edition, American ChemicalSociety Monograph Series No. 63, Reinhold Publishing Company, 1942.However, it is well recognized in the art that hypochlorite salts, asdesulfurizing agents, can only be used in strongly alkaline media.Adjustment of the pH to either the neutral point or an acid rangeresults in the liberation of free chlorine, and undesirable chlorinationof the oil thereby results.

On the other hand, the metal chlorites are effective desulfurizingreagents in either the neutral, acid or alkaline state and the activereagent is chlorine dioxide (C102) which is absent from any of thehypochlorite processes.

The effectiveness of my invention will be more clearly illustrated bythe following example:

Example 1 A paraffinic base oil having a viscosity of about 35 secondsUniversal Saybolt at 100 F. which had been treated to produce a whiteoil with fuming sulfuric acid, neutralized with sodium carbonate,alcohol washed to remove sulfonic bodies, and steamed to remove thealcohol, was found to be highly corrosive to copper.

The above acid-treated oil was refluxed at boiling temperature andatmospheric pressure with 10% by volume of a 0.1% by weight solution ofsodium chlorite for 1 hour. The layers were allowed to separate and theoil finished by a water wash and brightened by paper filtering. Theoriginal oil, without any treatment, showed a highly corrosive copperstrip rated as #9, and developed a rancid and garlic-like odor whenexposed for a short time to sunlight. After treatment with the chlorite,the oil gave a No. 1 copper strip test and exhibited satisfactorystability to sunlight. The spent chlorite liquor gave a positiveindication of sulfate ion being present when tested by standard method.

Numerous modifications may be made in the process by those skilled inthe art without departing from the scope of the invention described.

What is claimed is:

1. A process for preparing petroleum hydrocarbon oils non-corrosive tocopper which comprises treating the hydrocarbon oil with concentratedsulfuric acid ranging in strength from 98% sulfuric acid to fumingsulfuric acid having by weight of sulfur trioxide, removing the sludge,neutralizing the acid-treated oil with a neutralizing agent, extractingthe products of neutralization with an immiscible solvent, removingresidual immiscible solvent from the oil, and treating the resulting oilwith an aqueous solution of an alkali metal chlorite, and thereaftertreating the resulting oil with clay,

. v2. A'iprooess according toiclaimyl'iin'whieh th alkali metalchloriteisqsodium chlorite. :1;

3. A process for preparing YDEtITOIBQIXI-JIYGIOP. carbon oilnon-corrosive to copper which comprises treating the hydrocarbon oilwith concentrated sulfuric acid ranging in strength from 98% sulfuricacid to fuming sulfuric acid having 20%;byweight of sulfur trioxide,neutralizing the acid-treated oil with a neutralizing agent,v extractingtheproduct of neutralization with an immiscible solvent, removingresidual immiscible solvent from the oil and treating the resulting oilwith an aqueoussolutionof anaalkali metalichlorite-at a temperature of.from 40C. to aboutalOO" C. for a time of from about 20 minutes to 4hours and separating the oil from the aqueous solution, and thereaftertreating the resulting oil with clay.

4. A process for preparing petroleum hydro carbon oils non-corrosive tocopper which comprises treating the hydrocarbon oil with concentratedsulfuric acid ranging in strength from 98% sulfuric acid to fumingsulfuric acid having 20% by weight of sulfur trioxide, removing thesludge, neutralizing the acid-treated oil with a neutralizing agent,extracting the products of neutralization with an immiscible solvent,removing residual immiscible solvent from the oil, treating theresulting oil with clay, and treating the finished oil with an aqueoussolution of an alkali metal chlorite.

5. A process for preparing petroleum hydrocarbon oils non-corrosive tocopper which comprises treating the hydrocarbon oil with concentratedsulfuric acid ranging in strength from 98% sulfuric acid to fumingsulfuric acid having 20% by weight of sulfur trioxide, removing thesludge, neutralizing the acid-treated oil with a neutralizing agent,extracting the products of neutralization with an immiscible solvent,removing residual immiscible solvent from the oil, treating theresulting oil with clay, and treating the finished oil with an aqueoussolution of an alkali metal chlorite at a temperature of from 40 toabout 100 C. for a period of time from about 20 minutes to 4 hours andseparating the oil from the aqueous solution.

6. A process for preparing petroleum hydrocarbon oils non-corrosive tocopper which comprises treating the hydrocarbon oil with concentratedsulfuric acid ranging in strength from 98% sulfuric acid to fumingsulfuric acid having 20% by weight of sulfur trioxide, removing thesludge, neutralizing the acid-treated oil with a neutralizing agent,extracting the products of neutralization with an immiscible solvent,removing residual immiscible solvent from the oil, whereby said oil hasa good copper corrosion test, and treating the resulting oil with anaqueous solution of an alkali metal chlorite, and thereafter treatingthe resulting oil with clay.

'7. A process for preparing petroleum hydrocarbon oils non-corrosive tocopper which comprises treating the hydrocarbon oil with concentratedsulfuric acid ranging in strength from 98% sulfuric acid to fumingsulfuric acid having 20% by weight of sulfur trioxide, removing thesludge, neutralizing the acid-treated oil with a neutralizing agent,extracting the products of neutralization with an immiscible solvent,removing residual immiscible solvent from the oil, whereby said oil hasa good copper corrosion test, treating the resulting oil with clay,whereby said oil has a poor copper corrosion test, and

7 8 treating the finished oil with an aqueous solution Number Name Dateof an alkali metal chlorite, whereby said 011 has 2,110,283 ArchiboldMar. 8, 1938 a good copper corrosion test. 2,179,008 Campbell Nov. '7,1939 2,382,753 Treseder Aug. 14, 1945 CHARLES COHEN' 5 OTHER REFERENCESREFERENCES CITED Sachanen, Conversion of Petroleum, pages 337, 343-345347. Copyright 1940 by Reinhold Th f 11 f e o owing re erences are ofrecord in the Publis] Corn'New YorkN-Y' file of thls patent 10Kalichevsky et a1., Chemical Refining of Pe- UNITED STATES PATENTStroleum," page 198. Copyright 1942 by Reinhold Number Name DatPublishing Corp., New York.

1,908,273 Taylor May 9, 1933 2,028,998 Schulze et a1 Jan. 28, 1936

1. A PROCESS FOR PREPARING PETROLEUM HYDROCARBON OILS NON-CORROSIVE TO COPPER WHICH COMPRISES TREATING THE HYDROCARBON OIL WITH CONCENTRATED SULFURIC ACID RANGING IN STRENGTH FROM 98% SULFURIC ACID TO FUMING SULFURIC ACID HAVING 20% BY WEIGHT OF SULFUR TRIOXIDE, REMOVING THE SLUDGE, NEUTRALIZING THE ACID-TREATED OIL WITH A NEUTRALIZING AGENT, EXTRACTING THE PRODUCTS OF NEUTRALIZATION WITH AN IMMISCIBLE SOLVENT, REMOVING RESIDUAL IMMISCIBLE SOLVENT FROM THE OIL, AND TREATING THE RESULTING OIL WITH AN AQUEOUS SOLUTION OF AN ALKALI METAL CHLORITE, AND THEREAFTER TREATING THE RESULTING OIL WITH CLAY. 